Tobacco smoke filter



p 1969 BAUM ETAL TOBACCO SMOKE FILTER Filed Nov. 15, 1965 JNVENTOR. LEO BAUM BY ROBERT E KRUEGER TTORNEYS United States Parent O 3,468,316 TOBACCO SMOKE FILTER Leo Bam, Oakland, and Robert E. Krueger, Lafayette, Calif., assignors to Nixotene Corporation, Piedmont, Calif., a corporation of California Filed Nov. 15, 1965, Ser. No. 507,914 Int Cl. A24f 13/04, 7/04 U.S. Cl. 131-187 9 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to mechanical filters for filtering tobacco smoke, and more particularly to a filter comprising mechanical means impelling the smoke along a curvilinear path in a direction and at velocities productive of enhanced condensation and separaton of high molecular weight components of tobacco smoke.

Tobacco smoke has long been suspected of being harmful to the health of smokers, and a multtude of filters for cleansing or purifying tobacco smoke has been developed; many of these are commercially available.

These suspicions have recently been confirmed by the Surgeon GeneraPs Report on Health and Smoking (Department of Health and Welfare Bulletin No. 1103). The report cites considerable evidence linking smoking and various health hazards, particularly lung cancer, and identifies hundreds of compounds which are Components of smoke and are also known as potential carcinogens. On the basis of this and additional information in the report, there is no evidence that any of the filters available today offers any protection or removes any of these harmful ingredients in substantal quantities.

Accordingly, there is an urgent need for a filter capable of efficiently reducing the concentrations of the harmful ingredients in smoke.

The chief reason for difficulty of removal of harmful compounds and substances from the smoke, an extremely stable aerosol, is the fact that the several hundred known or suspected carcinogens have practically no common features which simply and etlectively distinguish them from the harmless and otherwise desirable ingredients of tobacco smoke.

However, in view of the serious nature of the health problem, it is proposed in accordance with the present invention to provide a filter means for separating as many of the higher-mass constituents from the carrier gas of the smoke sol as possible. The carrier gas of the smoke is comprised chiefiy of carbon dioxide, nitrogen, and water vapor.

Accordingly, it is a primary object of the present invention to provide a mechanical filter discriminating between the particles on the basis of their mass and momentum.

A further object of the present invention is to provide a conduit structure for producing curvilin'ear motion of vortiginous motion, superimposed on a spiral motion, to

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generate high differental angular momenta in smoke particles or Components of dilferent masses.

The present invention provides an efficient filter means for tobacco smoke, comprising a combination of structures for forming a smoke conduit imparting to the ciga rette smoke a motion characterized by velocty and directional properties most conducive to a separaton of the relatively high molecular weight vapors and heavy particle fractions of the smoke sol from the light weight and comparatively harmless vapors and gases of tobacco smoke.

A particular feature of the present invention is the conduit structure, which `comprises a series of passages and chambers which are critically interrelated both with respect to their relative sizes and as to the shapes of the surfaces. As the smoke passes from the cigarette or the like into the present filter, it is cooled and channelled into a narrow discoidal chamber. The smoke enters the chamber by way of one or more pinhole orifices, the precise dimension of which is critically interrelated with dimensions of the remainder of the conduit system: in particular, the thickness of the discoidal chamber, the"transconductance of the entire filter, and the dimensions of succeeding smoke channels in the conduit system. The jet of smoke entering the chamber impinges a baflle positioned transversely to the path of the smoke, causing the highest boiling temperature materials to cordense on the baffie. The deposition of these materials is enhanced by providing a heat sink for cooling the smoke prior to impingement.

Another feature of the present invention is the provision of a toroidal cooling chamber connected to the impingement chamber. The Volume of this cooling cham- -ber progressively expands inwardly and radially with increasing proximity to the mouthpece. The Volume gradient of the chamber is thus opposite the temperature and pressure gradients therein. The smoke enters the toroidal chamber through peripherally located inlet channels and is imparted a swirling motion about the conical inner boundary of the chamber, inducing the lateral deposition of some of the heavier constituents of the smoke. However, the smoke is primarily further cooled, in preparation for the elimination of vapors and particles condensing at still lower temperatures and characterized by still smaller particle sizes.

A further feature of the present invention is the provision of a succeeding chamber, which will be referred to as the vortex chamber for convenience. The vortex chamber is similar in nature to the cooling chamber, it being a toroidal affair of increasing radial width extending progressively toward the axis of the filter. The smoke inlet into the vortex chamber is a peripherally located convergent nozzle. The preferred orientation of the nozzle is at an angle to the axis of the filter, the nozzle axis pointing generally outwardly and in the direction of a left-hand spiral advancng in the direction of the axial flow of the smoke. The vortex nozzle thus points in the opposite direction of the natural swirling tendency of the smoke. Smoke entering the vortex chamber is subjected to conditions favorng passage of lighter particles, and tending to deposit the heavier Components onto the walls of the vortex chamber, which may be suitably coated for improving the adsorptive characteristics thereof.

Other objects, features of novelty, and advantages of the present invention will become apparent upon con- &468316 sideration of the following description of a preferred specific embodiment of the present filter means, illustrated in the drawings, of which:

FIGURE 1 is a longitudinal view of a cigarette filterholder in section,

FIGURE 2 is a cross-sectional view of a preferred terminal cup for holding a cigarette,

FIGURE 3 is a perspective view of a plug whose surfaces define the interior boundaries of the central portion of the smoke conduit through the present filter,

FIGURE 4 is a transverse cross-section, taken along the line 4-4, of the plug shown in FIGURE 3,

FIGURE 5 is a preferred filter Cartridge in crosssection.

The principal components of the cigarette filter shown in the drawings are tubular sleeve 10, constituting receptacle or ferrule 11, plug 12, and filter Cartridge 13, which are within the bore of sleeve in the order named. Ferrule 11 is generally cup shaped, adapted to hold the end of a cigarette. The geometry of plug 12 is essentially that of axially aligned and abutting conical frustra and cylindrical discs in alternating succession. The radially recessed surface of plug 12 together with the interior surface of sleeve 10 define a major portion of the smoke conduit through the filter including the impingement, cooling, and vortex chambers. Filter Cartridge 13 comprises a composite of fibrous, porous and/ or granular filter media, and may additionally include flavoring agents.

It should be realized that although the specific description deals only with the cigarette filter em'bodiment shown in the drawings, a filter for cigars or pipes may be readily provided by minor changes in the ferrule geometry to accommodate the end of a cigar or the outlet portion of the bowl of a smoking pipe. Moreover, the present filter may be used as an integral terminal filter within cigarettes or cigars, with appropriate changes in the dimensions of the conduit-defining Components of the filter, as will become clear hereinbelow upon discussion of the dimensional relations of the conduit passages. If incorporated directly into the body of a smoking article, such as a cigar Or cigarette, the filter is preassembled and joined to the end of the cigarette or cigar in a conventional manner. The cost penalties incurred by such use of the present filter are insignificant, since the present filter is comprised at the most of four parts, which may be economically manufactured from low-cost raw materials; e.g., injection molding a polyethylene plug and stamping an aluminum discoidal orifice plate corresponding to the bottom of cup-shaped receptacle 11. However, although the present filter is readily incorporated directly into .a smoking artiele, it is preferred to utilize the filter system in a separate cigarette or cigar holder, since the greater mass and physical size of such an auxiliary smoking implement contribute to the efficiency of filtration.

-Referring now to the cigarette holder illustrated in FIGURE 1, tubular sleeve 10 forms the outer structure of the cigarette holder and defines a cylindrical bore 14 and smoke passage 16 through tapered mouthpiece portion 17 at one end of said sleeve. The bore 14 at the opposite end of sleeve 10 is fitted with the cup shaped, flanged receptacle 11, which is recessed to define a socket 19 for holding a cigarette. The bottom portion 20 of receptacle 11 has a nipple 21 defining a central orifice 22. Orifice 22 is preferably the narrowest smoke passage of the entire filter conduit. Accordingly, the size of orifice 22 is a major factor determining the pressure drop across the entire filter, which establishes the amount of suction which the smoker has to apply to draw smoke through the filter. Specically, an orifice less than 6.1 (10- square inches in cross-sectional area (028" in diameter) has been found unsatisfactory, since it is too diflicult to draw smoke through the filter. On the other hand, if the central orifice is more than about 9.6 1O* square inches in cross-sectional area (.035" in diameter), the efficiency of the filtering action is seriously curtailed due to the reduced velocity and increased temperature of the smoke stream entering discoidal impingement chamber 23. This 'relatively higher temperature is caused by lesser adiabatic expansion of the smoke passing from the exceedingly hot burning zone of the cigarette into the filter, whence the smoke loses less of its heat energy to the environment prior to entering the filter conduit. For optimum results as to draw and cooling it is preferred that the orifice be circular and have a diameter between .O29" and .033". If instead of a single orifice 22, a multiplicity of orifices is provided, the area of the individual orifices must of course be reduced correspondingly to provide a total cross-sectional area within the above limits. Receptacle 11 is preferably made of a highly heatconductive metal, such as Copper or aluminum, or their alloys, whereby the heat-sink effectiveness of the receptacle is considerably enhanced. As best seen in FIGURE 2, an annular stepped surface 24 a'buts the end of cigarette 27, serving to seat the cigarette in spaced relation to the bottom 20 of the receptacle, thereby creating recessed chamber 28. Orifice 22 chokes the flow of smoke and causes smoke to accumulate and remain for a brief interval in the chamber 28. Although brief, the delay interval is suiciently long to allow considerable heat transfer from the hot smoke to the walls 29 and bottom 20 of metal receptacle 11. The heat is then dissipated by integral flange 31 and into sleeve 10.

The filter conduit portion between receptacle 11 and the mouth of the filter is defined by the surfaces of plug 12 and portions of the inner wall of sleeve 10. The conduit comprises at least four main chambers, discoidal impingement chamber 23, toroidal cooling chamber 32, toroidal vortex chamber 33, and the housing 34 for filter Cartridge 13, respectively, in the order of increasing distance from socket 19. The chambers 23, 32, and 33, and filter housing 34 are successively separated from one another by cylindrical disc portions 36, 37, and 38, respectively, said disc portions projecting radially from the body of plug 12. The transverse cross-sectional areas of the disc portions 36, 37 and 38 of plug 12 are equal to the cross-sectional area of bore 14.

Each portion is circumscribed by a feathered edge 39 to provide a tight fit between the plug 12 and sleeve 10, thereby scaling the plug to the sleeve and assuring that the separate chambers only communicate with one another as hereafter described. The precise shape of the chambers and communicatng Channels through the peripheral region of the disklike projecting portions 36, 37 and 38 will be readily apparent on a consideration of the geometry of plug 12, shown in detail in various sectional and perspective views in FIGURES 3, 4, and 5.

Terminal surface 41 of plug 12, facing receptacle 11, is maintained in parallel spaced relation to the bottom 20` of receptacle 11 by a plurality of raised spacers 42, projecting a predetermined distance from the terminal surface 41. The impingement chamber 23 is formed by bottom 20 of ferrule 11 and terminal surface 41. The pressure gradient developed across orifice 22 forces the smoke into chamber 23 at high velocity, sim'ultaneously condensing heavy smoke components through cooling by adiabatic expansion. The smoke jet impacts the transversely disposed terminal surface 41. The high velocity and rapid change of direction of the smoke stream causes the separation of heavy smoke Components, which are carried onto the surface by virtue of their high momentum and inertia. Copious quantities of a heavy, dark brown, viscous fluid are deposited onto surface 41. The degree of separation of this heavy tar from the smoke is critically depeudent upon both the orifice size and the spacing between surface 41 and orifice 22, as well as the temperature of the smoke, which should be as low as possible. It has been found that optimal rate of tar removal at this state is achieved with a spacing between surface 41 and orifice 22 between .025" and 035", and an orifice diameter of .029" to .033". It is to be noted that the provision of nipple 21 &468316 defining orifice 22 provides this optimum spacing while allowing the chamber 23 to have a relatively large capacity for the tar.

Cooling chamber 32 communicates with discoidal chamber 23 through channels provided by axially oriented, diametrically opposed recesses 44 in the peripheral region of protruding discodal portion 36. The interior surface of cooling chamber 32 is provided by the conical frustrum 47, which is an integral member of the plug 12, tapering rearwardly in the direction of travel of the smoke. The swirling motion of the smoke and the turbdity produced in the cooling chamber are indcated by the arrows. In addition to enchancing cooling, the swirl causes the discharge of a minor amount of contaminants onto the chamber walls. Furthermore, tar overflow from impingement chamber 23 can pass slowly through recesses 44 and collect in chamber 32, which also serves as an auxiliary reservoir.

Nozzle 48 converges in a ratio of about 6:1, based on the areas subtended by the entrance and exit apertures. The nozzle is generally pointed in the direction of the interior wall 14 of sleeve 10, i.e., away from the axis of the filter. Moreover, the nozzle is pointing toward the left is shown, to impart to the smoke a spiral motion about the axis of the plug. The vortex chamber 33 is torodal in character, similar to cooling chamber 32. However, frustrumlike member 49, tapered in the axial direction, is circumferentially asymmetric, having a spiral-like mantle 50, as may be seen from the cross-sectional View in FIGURE 4. The natural direction of the swirling motion of a vortex is toward the right. As may be seen in FIGURES 3 and 4, the surface of member 49 exhibits an axially extending stepped portion 51, to the right of the nozzle exit, aiding and guidng the flow of the smoke. The smoke stream makes about 1 /2 to 2 /2 turns in the vortex chamber before leaving through slanted exit slot 52, cut into discoidal member 38. The peripheral communicating channels 45, 48, and 52 between the chambers 23, 32, 33, and 34 are arranged in a nonaligned, staggered fashion, particularly vortex nozzle 48 and vortex chamber exit 52, which are diametrically opposed to one another. It will also be noted that the exit 52 is slanted in the direction of a right-hand spiral, whereas the vortex nozzle is oriented toward the left. The flow conditions through the filter means are optimized with respect to removal of heavy constituents and amount of suction required, if the area of exit aperture 53 of the convergent nozzle is approximately equal to the area of orifice 22.

The final treatment of the smoke occurs in the filter Cartridge 13, which is inserted into housing 34 (defined by the terminal surface 56 of plug 12, bore 14, and recess 57). A preferred filter 'Cartridge 58 is shown in FIGURE 6, comprisng a mixture of filter Component 59 of bonded activated charcoal granules, and a second component 61 of compacted acetate fibers. As mentioned previously, the filter Cartridge may be impregnated with a fiavorng or aroma-producing agent, to modify or restore the taste or odor of the smoke prior to its discharge into smoke outlet passage 16.

The cigarette filter described is readily made as a disposable item in View of the low cost of the product. Plug 12 can be made of polyethylene by injection molding; ferrule 11 from metal sheet by stamping with a suitable die; the outer sleeve may also be of a suitable thermoplastic material and injection molded; and filter Cartridge materials are commercially available as widely used in filter-tip cigarettes. However, it should be noted that the filter may also be made entirely of metal as a permanent item; that the filter can be readily disassembled and cleaned periodically, and the filter Cartridge may be exchanged. Such a filter offers a great heat capacity and conductivity, whereby the smoke is cooled most effectively with corresponding improvements in smoke filtration.

What is claimed is:

1. A filter for tobacco smoke, comprising: a tubular body defining terminal smoke inlet and outlet means and a central bore extending therebetween; a discoidal member including an orifice in the central region thereof, said member extending transversely across said bore; and a cylindrical plug within said bore and having annularly and perpherally recessed surfaces defining at least two recessed torodal chambers between said plug and said tubular body, the annular transverse cross sectional area of said torodal chambers tapering substantally uniformly radially inwardly with increasing distance from said smoke inlet means, said plug having slots in the peripheral surface portions thereof between said torodal chambers and in the peripheral surfaces between said torodal chambers and the ends of said plug, to define inlet and outlet passages for each of said chambers, the slot defining the inlet passage to one of said torodal chambers being a convergent nozzle, a torodal chamber following a convergent nozzle being circumferentially asymmetric to produce a vortex action in the smoke, said plug being disposed within said bore in close-fitting relaton to the internal wall defining the same, one of the ends of said plug being parallel to said discoidal member and in closely spaced predetermined relaton thereto.

2. The filter of claim 1 further defined in that said orifice has a cross sectional area between about 6.1 10- square inches and 9.6 1O- square inches.

3. The filter of claim 1 further defined in that the distance between said orifice and the end of said plug is about 030".

4. The filter of claim 1 further defined in that said inlet and outlet passages defined by said slots are arranged about the periphery of said plug in a staggered pattern.

5. A filter for tobacco smoke, comprising: a tubular body defining terminal smoke inlet and outlet means and a central bore extending therebetween; a metallic ferrule having a bottom and fitted into the terminal smoke inlet end of said body and defining a socket for holdng a cigarette, the bottom of said ferrule defining an orfice in the central region thereof of a cross-sectional area between about 6.1 10* square inches and 9. 6 10- square inches; a removable cylindrical plug Wthn said bore and having annularly and perpherally recessed surfaces defining at least two torodal recessed chambers between said plug and said tubular body each having an essentially right-triangular cross-section along the principal axis thereof with said bore being one of the legs of the section and another leg being at right angles to said bore and being away from the smoke inlet means, said plug having slots extendng from the peripheral surfaces into the interior of said plug defining inlet and outlet passages for each of said chambers for the communication of smoke therethrough, the slot defining the inlet passage to the torodal chamber proximate said smoke outlet being a convergent nozzle inclined to the axis of said filter, the remainder of said slots being peripherally arranged about the slot defining said convergent nozzle in a staggered pattern; the torodal chamber following said convergent nozzle being circumferentially asymmetric to produce a vortex action in the smoke; said plug being disposed within said bore in close fitting relaton thereto, one of the end portions of said plug being parallel to the bottom of said ferrule and extending transverse to the orifice exit therein at a distance of about .025" to 035".

6. The filter of claim 5 further defined in that said toroid of chamber proximate said smoke outlet is defined by a spiral-lke recessed surface which has a raised -portion adjacent said convergent nozzle to preferentially &468316 7 8 8. The filter of claim 5 further defined in that said 3,167,076 1/ 1965 Mare 131-210 X nozzle exit has a cross-sectonal area about equal to the 3,174,487 3/ 1965 Mssler 131-187 area of said orifice.

9. The filter of claim S further defined in that said FOREIGN convergent nozzle has an exit to entrance transverse area r 12,228 Of 1910 Great B j ratio of about 5 to 1 0 5,685 3/ 1910 Great Brtain. 281,607 4/1928 Great Britain. References Cited 929,086 6/ 1963 Great Britain. UNITED STATES PATENTS 570698 12/1957 Italy- 879,79 2/1 8 Plane 1 1- 1 10 JOSEPH s. REICH, Prmary Examner 1,261,038 4/1918 Labreche 131-210 2,287,436 6/1942 Kom et al. 131-210 U.S. CI. X.R. 3,137,303 6/1964 ShaW 131-187 131-210 

